I. Field of the Invention
The invention relates to a delivery system for agriculturally active chemicals. More particularly, the invention relates to an emulsifiable concentrate of difficult to dissolve agricultural chemicals making use of biodegradeable solvents.
II. Description of the Prior Art
Agricultural chemicals are most preferably applied in the form of aqueous emulsions, solutions, or suspensions. Occasionally, they may also be applied in the form of a dust wherein the active ingredient is adsorbed onto or mixed with a finely divided inert carrier material, such as, china clay, or the like. With such powdered or dust compositions, drift due to wind is a problem and consequently, liquid formulations are preferred.
One of the problems with such liquid formulations is the fact that chemicals having agricultural activity often exhibit extreme insolubility in water. This results in their having to be dissolved either in organic solvents or utilized in the form of emulsions or suspensions. With respect to the use of organic solvents, these are generally disadvantageous from an environmental and cost viewpoint. Particularly, such organic chemicals may exhibit toxicity or side-effects which may be adverse to the effect of the agricultural chemical itself or to the subsequent fruit or vegetable produced in the particular agricultural use. This toxicity may also be disadvantageous with respect to handling.
When attempts are made to provide emulsified or suspension formulations, difficulties are encountered with respect to providing a desirably high concentration of the agriculturally active ingredient. Thus, when such agriculturally active chemicals are formulated into an emulsion, it is difficult to maintain the emulsified state. This makes it difficult to maintain a uniform formulation, particularly, when the formulation is diluted with water for application to the plants.
Typically, for example, the agriculturally active ingredient is mixed with one or more of a variety of conventional solvents and an emulsifying agent to form a concentrate. This concentrate may be an emulsion, suspension, or solution. The concentrate is then stored until it is transported to the site of use or may simply be transported and stored at the site of use. In any event, the concentrate normally will undergo some period of storage until it is ready for use. Understandably, it is most desirable to be able to transport the agriculturally active ingredient at the highest concentration possible so as to minimize the volume of material which need be transported. By the same token, however, at the use site, it is normally not feasible to admix ingredients together or to process them other than to dilute the concentrate with water. Accordingly, it is important that the concentrate emulsify easily, i.e., exhibit good "bloom", upon the addition of water. In addition, at the use site, it is often necessary to store the diluted concentrate for extended time periods until the actual application to the plants. Consequently, it is important that the diluted form of the concentrate exhibit good stability with respect to the uniformity of the emulsion and to avoid precipitation of the active ingredients. If non-uniformity or precipitation occurs in the diluted form, then non-uniformity will result in the application of the diluted formulation to the plants.
An attempt to provide concentrates of agriculturally useful chemicals is disclosed in South African Patent Application No. 695,393, filed Jul. 25, 1969. This application is directed to the formulation of a concentrate substantially water-insoluble pesticides for agricultural use. The pesticides, either in oil or solid form, are mixed with pyrrolidones having a hydrogen or a lower alkyl group containing from 1 to 4 carbon atoms attached to the nitrogen atom of the pyrrolidone ring. The application discloses that concentrated solutions of difficult to dissolve pesticides could be formulated and that such concentrates exhibited good stability. The concentrates utilized are those containing the pesticidal active ingredient, the particular lower alkyl pyrrolidone, a co-solvent which is usually a common organic solvent, such as, an aromatic including xylene, methylated and polyalkylated naphthalenes and aliphatic solvents, and a dispersing or emulsifying agent, such as, a surfactant, including polyoxyethylene alkylphenols, polyoxyethylene fatty esters, polyoxyethylene sorbitan fatty esters which may be blended with oil-soluble sulfonates, calcium and aminosulfonate salts, and the like.
This prior art does not offer a solution to the problem arising from the difficulty in maintaining the stability of the emulsion after the concentrate is diluted with water. Consequently, unless the diluted form of the concentrate is used immediately after emulsification, it is difficult to provide a stable diluted formulation for application to the plants.
In addition, for such agricultural uses, it is desirable to avoid the use of toxic solvents, including those of Lists 1 and 2 of 40 C.F.R. 154.7 dated Apr. 22, 1987, which includes inerts of toxicological concern and solvents having high flash points, as well as to increase the amount of the agriculturally active material in the concentrate. Moreover, many organic solvents which have been used in the past, even those exhibiting relatively low toxicities, are not biodegradeable and thus remain as a pollutant.